This invention relates to a process for highly stereospecific polymerization of .alpha.-olefins, such as ethylene, propylene, butene-1, etc., particularly propylene, with high activity. More particularly, it relates to a process for the production of highly stereospecific poly-.alpha.-olefins in a process having excellent polymerization activity, which comprises polymerizing an .alpha.-olefin in the presence of a catalyst comprising a specific activated titanium catalyst component and an organoaluminum compound.
A Ziegler-Natta catalyst comprising a compound of a transition metal belonging to Group IV to VI and an organic compound of a metal belonging to Group I to III of a periodic table has been in widespread use for polymerization of olefins. When polymerizing propylene using titanium trichloride and diethylaluminum chloride, the polymerization activity is not sufficiently high although the yield of the stereospecific polymer which is insoluble in heptane is very high, and thus it is necessary to remove the catalyst residue from the polymer product. A number of methods for polymerizing propylene by the use of a solid catalyst, which is prepared by supporting titanium tetrachloride on a support, such as a magnesium compound, and a triethylaluminum type catalyst, have been proposed. In accordance with these methods, however, the stereospecific property of the polymer product is not sufficiently high although the polymerization activity is very high.
Thus, in general, the polymerization activity of a catalyst and the stereospecific property of the polymer product are antipodal to each other and it has been believed that it is very difficult to improve both the polymerization activity and stereospecific property to high levels at the same time. No method has been proposed which is improved to the extent that both the polymerization activity and stereospecific property are satisfactory.
It is an object of the invention to overcome the prior art defects and to provide a method which increases both the polymerization activity and the stereospecific property of the polymer to high levels.